Technical Field
This disclosure relates to a method of trimming an electronic or microelectronic mechanical component to set its value or some other parameter to within a desired range of values, and to components trimmed by this method.
Description of the Related Technology
The processing steps used in the formation of integrated circuits, or of microelectrical mechanical components (MEMS) using integrated circuit fabrication techniques, can suffer from variations from one wafer to the next, or variations from one component to another across a wafer. Such variations may result in relatively small changes to the width of components formed by the microfabrication techniques, or change the relative alignment between different structures within a component. Similarly doping levels may vary from wafer to wafer.
As a result of these variations, the absolute values of components, such as the resistance of a resistor, or the mass of a resonant structure, such as a suspended beam or other component, may vary from integrated circuit to integrated circuit. This variation can occur even when the integrated circuits are supposed to be notionally identical.
The designers of integrated circuits and microelectromechanical systems devices (MEMS) often seek to rely on relative differences between components to make the circuit or structure work rather than relying on the absolute value of a component. Such a technique makes the circuits or MEMS devices relatively insensitive to process variations.
However, occasions still arise where a component should have a known and predetermined value or parameter. In such circumstances, it is known to trim components, for example by laser trimming, to set the required parameter of the component to a desired value give or take an acceptable margin of tolerance. However, trimming a component at a probe stage may still subject the integrated circuits to variation. For example, the absolute value of a parameter of a trimmed component (such as its resistance) may vary post trimming because the wafer is not hermetically sealed until it is packaged. Furthermore the act of packaging the semiconductor die may subject it to stresses that vary the parameter of the trimmed component.